Process for producing a worked gold alloy



3,117,864- PRGCEdS FGR PRODUCDJG A WQRIQID GGLD ALLOY Edward G. Heathand Colin R. Yates, Kings Cross, London, England; said Heath asslgnor toWestinghouse llralte 8: Signal Company Limited, London, England, acompany of Great Britain No Drawing. Filed Get. 20, 1961, Ser. No.145,433 Claims priority, application Great Britain Oct. 2 1960 3 Claims.(Cl. 75-135) The present invention relates to an alloy of gold, silicon,and antimony having relatively good ductility and substantially uniformcomposition and a process for producing the same.

Heretofore it has been found highly difi-lcult to produce sound workedmembers comprising an alloy of gold, silicon and antimony. Gold andsilicon alone have a tendency to segregate at the grain boundarie whenattempts are made to alloy the same by melting and casting. Whenantimony also is present, the tendency to segregate is increased andmany fissures are formed during casting of the ternary alloy. When thecast alloy is rolled or worked to shape, the fissures cause the memberto crack thus rendering the final product useless.

The object of the present invention is to provide a sound worked alloymember comprising predetermined proportions of gold, silicon andantimony, the alloy being characterized by relatively good ductility andsubstantially uniform composition.

Another object of the invention is to provide a process for producing asound Worked member comprising an alloy of gold, silicon and antimonyhaving substantially uniform composition, the steps comprising meltingthe constituents of the alloy in a non-oxidizing atmosphere, rapidlycooling the alloy in a shallow mold, anneaing the alloy and hot rollingthe same under non-oxidizing conditions.

Other objects of the invention will, in part, be obvious and will, inpart, appear hereinafter.

In accordance with the present invention and in attainment or" theforegoing objects, there is provided a sound worked member comprising analloy having predetermined proportions of gold, silicon and antimony ofsubstantially uniform composition and having relatively good ductility.The silicon and antimony may comprise from 0.01 to 10% each in thealloy. An alloy ingot is pre pared by heating desired proportions ofeach component or" the alloy in crucible tothe melting temperature ofthe alloy under an inert atmosphere or vacuum. The melt is then pouredinto a precooled shallow crucible in order to cause rapid solidificationthereby sustantiall eliminating the tendency of the components in thealloy to segregate. The ingot is then remelted in a nonozddizing bath,such as, silicone oil at a temperature slightly in excess of the solidustemperature of the alloy. The second alloy melt is then poured into athin walled metal mold immersed in an oil bath to cause the alloy tosolidify very rapidly and to cool at rate of approximately 100 C. persecond. The alloy casting is then annealed at an elevated temperatureslightly below the melting temperature for a time suitable to obtain thedesired grain structure. The alloy member is then rolled a temperatureabout or slightly above 300 until a thin foil of the order of 1 to 3mils thick is obtained.

The rolled gold-silicon-antirnony alloy in foil pellet or other shapes iespecially useful in making semiconductor devices wherein the antimonycomprises an n-type doping material.

The following example is illustrative of the invention.

An alloy was prepared by melting 129 grams of gold, 3.995 grams ofsilicon and 0.1318 gram of antimony in ire States Patent 0 3,ll7,3bdPatented Jan. 14, 1984 a silica crucible While under an argon atmosphereat a pressure of 200 millimeters of mercury and a temperature of 1100 C.After a period of time sufiicient to melt the alloy and cause completesolution of the constituents, the temperature was lowered to about 1,000C. and the alloy was poured into a water cooled stainless steel moldhaving internal dimensions of 1%. inch by inch by /2 inch.

Thi ingot was rernelted in a bath of silicone oil at a temperature of380 C. (-10 C. in excess of the sol-idus temperature) and allowed toflow into a steel mold. The steel mold was immersed in a bath ofsilicone oil held at room temperature and the mold had a depth ofapproximately 0.06 inch and a wall thickness of less than 0.01 inch sothat as the molten alloy is poured into the mold in the bath of oil, avery rapid solidification or" the alloy takes place owing to the rapidheat transfer to the oil bath. An estimated rate of cooling through theeutectic temperature (370 C.) was approximately 100 C. per second.

The alloy member was then annealed 30 minutes at 300 C. and then rolledat a temperature of from 300 C. to 320 C., oxidation of the alloy memberbeing prevented by a thin film of silicone oil which was allowed toadhere to the alloy member surface. The alloy member is then annealedagain for a period or" 20 minutes at 300 C. and subsequently rolled, thesequence being continued until a foil of approximately 0.002 inchthickness was obtained. By this means, a length of foil in excess of 3feet was successfully prepared.

it is intended that the above description be interpreted as illustrativeand not limiting.

We claim as our invention:

1. A process for producing a worked member comprising an alloycomprising from 0.01% to 10% of silicon, from 0.01% to 10% antimony andthe balance being gold, of substantially uniform composition and havingrelative- 1y good ductility, the steps comprising melting theconstituents of the alloy in a crucible in an inert atmosphere at anelevated temperature to insure complete dissolution of saidconstituents, rapidly solidifying the melt to preclude segregation ofthe constituents the grain boundaries, annealing the soli ified memberand hot working the member under non-oxidizing conditions.

2. A process for producing a worked member comprising an alloycomprising from 0.01% to 10% of silicon, from 0.01% to 10% antimony andthe balance being gold, of substantially unifonm composition and havingrelatively good ductility, the steps comprising melting the constituentsof the alloy in a. silicon crucible under an atmosphere of pure dryargon to insure compl te dissolution of said constituents, rapidlysolidifying the melt in a bath of silicone oil to preclude segregationof the constituents at the grain boundaries, anneadng the solidifiedmember at a temperature of about 300 C. for about 30 minutes and hotrolling the member at a temperature of iron 300 C. to 320 C.

3. A process for producing a worked member comprising an alloycomprising from 0.01% to 10% of silicon, from 0.01% to 10% of antimonyand the balance gold substantially uniform composition and havingrelatively good ductility, the steps com-prising melting theconstituents of the alloy in a silica crucible under an atmosphere ofpure dry argon at a pressure or" about 200 mm. of mercury and atemperature of about 1100 C. solidifying the melt in a precooled mould,remelting the solidified member in a bath of silicone oil at atemperature of about 380 C., rapidly solidifying the melt in a bath ofsilicone oil to preclude segregation of the constituents at the grainboundaries, annealing the member for about 30 minutes and rolling thesame at a temperature of about 30 C. in a silicone oil bath and con-Metals and Solidifications, A.S.M., Cleveland, pp. 201 and 203.

Form et al.: solidification of Metals, Modern Castings, vol. 37, April1960, pp. 151 and 153.

Smith: Principles of Physical Metallurgy, Harper & Bros, publishers,N.Y., 1956, page 324.

Beck: Technology of Magnesium and Its Alloys, Hughes & Co. Ltd, London,1940, page 322.

1. A PROCESS FOR PRODUCING A WORKED MEMBER COMPRISING AN ALLOYCOMPRISING FROM 0.01% TO 10% OF SILICON, FROM 0.01% TO 10% ANTIMONY ANDTHE BALANCE BEING GOLD, OF SUBSTANTIALLY UNIFORM COMPOSITION AND HAVINGRELATIVELY GOOD DUCTILITY, THE STEPS COMPRISING MELTING THE CONSTITUENTSOF THE ALLOY IN A CRUICIBLE IN AN INERT ATMOSPHERE AT AN ELEVATEDTEMPERATURE TO INSURE COMPLETE DISSOLUTION OF SAID CONSTITUENTS, RAPIDLYSOLIDIFYING THE MELT TO PRECLUDE SEGREGATION OF THE CONSTITUENTS THEGRAIN BOUNDARIES, ANNEALING THE SOLIDIFIED MEMBER AND HOT WORKING THEMEMBER UNDER NON-OXIDIZING CONDITIONS.